BACKGROUND: The de novo generation of patient-specific hematopoietic stem and progenitor cells from induced pluripotent stem cells (iPSCs) has become a promising approach for cell replacement therapies in the future. However, efficient differentiation protocols for producing fully functional human hematopoietic stem cells are still missing. In the mouse model, ectopic expression of the human homeotic selector protein HOXB4 has been shown to enforce the development of hematopoietic stem cells (HSCs) in differentiating pluripotent stem cell cultures. However, the mechanism how HOXB4 mediates the formation of HSCs capable of long-term, multilineage repopulation after transplantation is not well understood yet. METHODS: Using a mouse embryonic stem (ES) cell-based differentiation model, we asked whether retrovirally expressed HOXB4 induces the expression of Runx1/AML1, a gene whose expression is absolutely necessary for the formation of definitive, adult HSCs during embryonic development. RESULTS: During ES cell differentiation, basal expression of Runx1 was observed in all cultures, irrespective of ectopic HOXB4 expression. However, only in those cultures ectopically expressing HOXB4, substantial amounts of hematopoietic progenitors were generated which exclusively displayed increased Runx1 expression. CONCLUSIONS: Our results strongly suggest that HOXB4 does not induce basal Runx1 expression but, instead, mediates an increase of Runx1 expression which appears to be a prerequisite for the formation of hematopoietic stem and progenitor cells.
BACKGROUND: The de novo generation of patient-specific hematopoietic stem and progenitor cells from induced pluripotent stem cells (iPSCs) has become a promising approach for cell replacement therapies in the future. However, efficient differentiation protocols for producing fully functional human hematopoietic stem cells are still missing. In the mouse model, ectopic expression of the human homeotic selector protein HOXB4 has been shown to enforce the development of hematopoietic stem cells (HSCs) in differentiating pluripotent stem cell cultures. However, the mechanism how HOXB4 mediates the formation of HSCs capable of long-term, multilineage repopulation after transplantation is not well understood yet. METHODS: Using a mouse embryonic stem (ES) cell-based differentiation model, we asked whether retrovirally expressed HOXB4 induces the expression of Runx1/AML1, a gene whose expression is absolutely necessary for the formation of definitive, adult HSCs during embryonic development. RESULTS: During ES cell differentiation, basal expression of Runx1 was observed in all cultures, irrespective of ectopic HOXB4 expression. However, only in those cultures ectopically expressing HOXB4, substantial amounts of hematopoietic progenitors were generated which exclusively displayed increased Runx1 expression. CONCLUSIONS: Our results strongly suggest that HOXB4 does not induce basal Runx1 expression but, instead, mediates an increase of Runx1 expression which appears to be a prerequisite for the formation of hematopoietic stem and progenitor cells.
Authors: Bernhard Schiedlmeier; Ana Cristina Santos; Ana Ribeiro; Natalia Moncaut; Dietrich Lesinski; Herbert Auer; Karl Kornacker; Wolfram Ostertag; Christopher Baum; Moises Mallo; Hannes Klump Journal: Proc Natl Acad Sci U S A Date: 2007-10-16 Impact factor: 11.205
Authors: Maria E Alonso-Ferrero; Niek P van Til; Kerol Bartolovic; Márcia F Mata; Gerard Wagemaker; Dale Moulding; David A Williams; Christine Kinnon; Simon N Waddington; Michael D Milsom; Steven J Howe Journal: Exp Hematol Date: 2017-09-11 Impact factor: 3.084
Authors: Nadine Teichweyde; Lara Kasperidus; Sebastian Carotta; Valerie Kouskoff; Georges Lacaud; Peter A Horn; Stefan Heinrichs; Hannes Klump Journal: Stem Cell Reports Date: 2018-02-15 Impact factor: 7.765